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NGC-4889 (Caldwell 35) Coma Berenices Galaxy Cluster Introduction the Purpose of the Observer’S Challenge Is to Encourage the Pursuit of Visual Observing

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NGC-4889 (Caldwell 35) Coma Berenices Galaxy Cluster Introduction the Purpose of the Observer’S Challenge Is to Encourage the Pursuit of Visual Observing MONTHLY OBSERVER’S CHALLENGE Las Vegas Astronomical Society Compiled by: Roger Ivester, Boiling Springs, North Carolina & Fred Rayworth, Las Vegas, Nevada With special assistance from: Rob Lambert, Las Vegas, Nevada April 2010 NGC-4889 (Caldwell 35) Coma Berenices Galaxy Cluster Introduction The purpose of the observer’s challenge is to encourage the pursuit of visual observing. It is open to everyone that is interested, and if you are able to contribute notes, drawings, or photographs, we will be happy to include them in our monthly summary. Observing is not only a pleasure, but an art. With the main focus of amateur astronomy on astrophotography, many times people tend to forget how it was in the days before cameras, clock drives, and GOTO. Astronomy depended on what was seen through the eyepiece. Not only did it satisfy an innate curiosity, but it allowed the first astronomers to discover the beauty and the wonderment of the night sky. Before photography, all observations depended on what the astronomer saw in the eyepiece, and how they recorded their observations. This was done through notes and drawings and that is the tradition we are stressing in the observers challenge. By combining our visual observations with our drawings, and sometimes, astrophotography (from those with the equipment and talent to do so), we get a unique understanding of what it is like to look through an eyepiece, and to see what is really there. The hope is that you will read through these notes and become inspired to take more time at the eyepiece studying each object, and looking for those subtle details that you might never have noticed before. Each new discovery increases one’s appreciation of the skies above us. It is our firm belief that careful observing can improve your visual acuity to a much higher level that just might allow you to add inches to your telescope. Please consider this at your next observing session, as you can learn to make details jump out. It is also a thrill to point out details a new observer wouldn’t even know to look for in that very faint galaxy, star cluster, nebula, or planet. NGC-4889 (Caldwell 35) Coma Berenices Galaxy Cluster NGC-4889, also known as Caldwell 35, is a super-giant Class-4 elliptical galaxy in the Coma galaxy cluster. It’s the brightest member of the group and lies approximately two hundred and fifty million light years away. With a relatively dim mag. 11.4, it’s sometimes drowned out by the glare from the nearby mag. 7 star, Beta Comae Berenices, especially if the sky conditions are not good. Nearby is the second brightest galaxy in the group, NGC-4874 at mag. 12.6. Observations/Drawings/Photos Roger Ivester: Observer from North Carolina My favorite deep-sky objects have always been galaxies. The April Challenge object, NGC-4889 is the brightest galaxy in the Coma cluster. This elliptical galaxy glows rather faintly at mag. 11.4 and can be difficult if conditions are not very good. All of my observations were made from my moderately light-polluted backyard located in Boiling Springs, North Carolina, which is in the foothills region of the western part of the state. I used two telescopes for my observations including a 10-inch f/4.5 reflector and a 4-inch f/9.8 refractor. The following observations were made over a three night period with the seeing and transparency both being rated as fair to poor. The naked eye limiting magnitude for these nights averaged 5.0 to 5.5, which can be normal for this time of the year due to higher humidity, and haze. With the 10-inch, NGC-4889 at 143X was faint, slightly elongated with an orientation of E-W. I saw a bright stellar nucleus with averted vision, but couldn’t hold it constantly. A faint and also elongated halo surrounded the galaxy, and it was fairly easy to see. I also observed it with the 4-inch refractor, which presented NGC-4889 as elongated with a brighter and more concentrated middle, but without a stellar nucleus. The second brightest galaxy of the Coma cluster is NGC-4874, and is located less than 10’ away from NGC-4889, toward the west. NGC-4874 is especially difficult, being located south of a bright mag. 7 star which causes significant glare. NGC-4874 shines at a fainter mag. 11.9, and the surface brightness is fairly low, with a mostly even texture, without any central brightening. Wanting to see more, I decided to borrow a 13mm eyepiece from a local observatory for a trial. When using the 13mm eyepiece with the 10-inch, it gave a magnification of 87X. I was very surprised to see that the glare was completely eliminated as compared to the views of the four-element eyepiece from the previous night. The 13 mm did not have any internal reflections and much greater detail was now visible. The view of NGC-4874 was now mostly round, very little concentration, an even texture with a faint, but very subtle brighter core. I noted that the background in the larger field of the 13 mm was much darker and also the bright mag. 7 star was no longer distracting. I also observed both galaxies with my 4-inch refractor, and to my surprise, NGC-4874 was actually easier to see than with the 10-inch. The glare of the mag. 7 star was far less with the refractor as compared to the much larger reflector, when using the four-element eyepiece with internal reflections, as discussed in the previous paragraph. The contrast of the much smaller refractor was superior, and fainter detail could be observed. When observing with the 4- inch, NGC-4874 appeared mostly round, very soft and even texture, a very faint halo, and I noted no central brightness. I was not able to use the 13mm with the refractor due to time constraints the following night. Fred Rayworth: Observer from Nevada I observed this galaxy the same night I spotted the March challenge objects, in early April with my 16-inch f/4.5 Dobsonian and 26mm (70X), 17mm (101X) and 8mm (229X) eyepieces. However, the sky conditions were horrible to the east that night. Besides some kind of haze that was in the sky, two derrick barges out in the middle of Lake Mead were covered with spotlights and lit up the sky worse than the moon would have. Those lights caused a glow that at first didn’t seem that bad until I tried to find any galaxies in the Coma Berenices/Virgo/Leo part of the sky. Before I concentrated on NGC-4889, I succeeded with a couple of brighter galaxies in Ursa Major and Leo and barely saw objects at mag. 10, despite the sky appearing dark above the glow coming off the lake. After much hunting and pecking, I only found NGC-4889 because I knew exactly where to look. It took several passes before I spotted it and could see almost nothing with direct vision. With averted vision, I spotted an oval shape that didn't look quite right. At 229X, it showed a slight lump to one side which may have been NGC-4886. What bothered me was that it shouldn’t have looked like an oval, being an elliptical galaxy. I was expecting a rounder shape or at least a fatter oval with a fuzzy glow like a distant globular cluster. I took my bearings again to make sure the star was Beta Comae Berenices and looked again, saw the same thing. NGC- 4874 which should have been clearly visible right next to it was not there at all. After looking at photographs, I recognized the star patterns and positively identified the area. On a better night, I should’ve seen multiple galaxies in the field of view. This was a shock after seeing so much detail in the March object which was in the skyglow of Las Vegas. My sketch reveals an empty field of stars except for the oblong lumpy fuzz of NGC-4889 and NGC-4886. I even doubted the lump I saw was really NGC-4886 as it is much fainter than NGC-4874. However, it is also much smaller and concentrated so that may be why I was able to spot it. Dr. James Dire: Observer from North Carolina Galaxies tend to group into galaxy clusters. Many are found throughout the heavens. Perhaps one of the most impressive galaxy clusters is the Coma Cluster in the constellation Coma Berenices. The coma cluster contains approximately 1,000 galaxies located roughly 300 million light years away. The cluster can be found approximately one-quarter of the way along the line from the mag. 4 star Beta Comae Bernices to the mag. 4 star Gamma Comae Bernices. My cluster image is centered on NGC-4889, the brightest galaxy in the cluster. NGC- 4889 is a not-so-impressive mag. 11 elliptical galaxy that’s roughly half the size of our Milky Way home. NGC-4889 is not only the brightest member of the cluster, but it’s also located near the center of the cluster from our perspective. My image spans the inner 1° field of view around NGC-4889. There are several Milky Way stars in this field of view. The brightest is mag. 7 HD112887. Most of the faint objects in the image are galaxies. I estimate that 200-300 galaxies are visible in this 3 hr exposure taken with a 190mm (7.5-inch) f/5.3 Maksutov-Newtonian astrograph with an SBIG ST-2000xcm CCD camera.
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